Apparatus for processing printing plates precoated on one side only

ABSTRACT

This invention relates to a dispensing apparatus for lithographic developer comprising bar means adapted to extend across a printing plate to be developed, slot means in the bottom of said bar means, means for supplying developer under pressure to said slot means, and means for reciprocating said bar means transversely to the direction of plate travel.

NJ. 07871; Robert C. Graham, 10 Pierson Ln., Florham Park, NJ. 07932July 27, 1971 (Under Rule 47) Appl. No: 166,474

[22] Filed:

[56] References Cited UNITED STATES PATENTS 2.677.320 5/1954 Coughlin95/89 R United States Patent 1191 1111 3,903,541 Von Meister et al.Sept. 2, 1975 [54] APPARATUS FOR PROCESSING PRINTING 2,956,494 10/1960Tyler et a1 118/410 UX PLATES PRECOATED ON ONE SIDE ONLY 3,066,04711/1962 Mahoney 118/120 X 3,081,687 3/1963 Takats 95/89 R [76]Inventors: Frederick W. Von Meister, WlllOW 3,338,149 8/1967 Hemery95/89 R Ave., Peapack, NJ. 07977; Eugene 3,354,807 11/1967 Homer 95/89 RX J. Gaisser, Jr., 2 Circle Ten, Sparta, 3,593,641 7 1971 Adams et a1118/120 x Primary Examiner-Richard L. Moses Attorney, Agent, or Firm-James E. Bryan and means for reciprocating said bar meanstransversely to the direction of plate travel.

ABSTRACT 4 Claims, 3 Drawing Figures DEVELOPER SUPPLY LINE DEVELOPERSUPPLY RECIPROCATOR 38 SHAFT J/VOLLME REGULATOR SPREADER BLADEPHETZTETESEP EH75 3 903541 SHEET 2 U? 3 FIG. 2

8 TRANSPORT ROLLS DEVELOPER PLATE TRAVEL RECIPROCATOR SHAFT E SUPPORTHEAD RAIL INVENTORS FREDERICK W. von MEISTER ENE J. GAISSER, JR.

R ERT C. GRAHAM ATTORNEY PATENTEU 2W5 3.963 541 SEZCET 3 OF 3 DEVELOPERSUPPLY LINE RECIPROCATOR 38 SHAFT SPRING IIII 1 1 INVEN FREDERICK W. vonMEI EUGEEE J GAlSSER,J

ROB c. GRAHAM A TORNEY APPARATUS FOR PROCESSING PRINTING PLATESPRECOATED ON ONE SIDE ONLY This invention relates to an apparatus forprocessing a printing plate precoated on one side only, and moreparticularly relates to a dispensing apparatus for lithographicdeveloper.

It has long been known in the lithographic industry that a subtractivepresensitized offset printing plate may be developed by what is known asthe hand developing process. In this process the carrier, which isusually a thin sheet of aluminum, is first coated by the manufacturerwith a light-sensitive coating usually containing, among other things,one or more resins, and the plate is then sold in the presensitizedcondition to the customer.

The customer exposes the printing plate through a stencil to a source ofstrong light, such as a carbon are for example. The lightsensitivecoating when subjected to such a light is converted in such a mannerthat, after development, the image areas are retained on the platesurface and the non-image areas are removed. After development, forexample by rubbing a developing agent into the surface of the plate bymeans of a sponge, the plate may be fixed and/or washed and, finally. acoating of gum arabic or similar material is applied to the surface ofthe plate to protect the image free areas thereof. The plate is thenready for the printing press.

More specifically, where this hand developing process is employed toproduce a printing plate, the following procedure is generally followed:From a typewritten setup or makeup, equivalent to the material to beprinted and provided in any desired manner including typed articles.pictures of various kinds of art work of different sizes, and the like,all assembled onto a suitable cardboard or other support, a master isprepared in the conventional manner. The image of the master is thentransferred onto the sensitized printing member, such as is describedabove, by a suitable exposure means.

The printing member thus prepared is then subjected to a developingoperation using the chemistry prescribed by the manufacturer of theprinting member. This chemistry" is worked into the exposed coating byhand rubbing, for example with a sponge, until the nonimage areas aresubtracted or removed from the carrier leaving an exact replica of theimage on the plate carrier. The printing member is then fixed and/orwashed and a solution of gum arabic, or a similar solution, is appliedto the plate surface, resulting in a printing plate which is ready forthe press.

The disadvantages of hand development of offset printing plates arenumerous. The process is slow and expensive. Uniformity of pressure inapplying the de veloping solution to remove the undesired coating isalmost impossible to attain and exposure to the developing solution isuneven. Thus, defective printing often results from an inadequatedevelopment or underdevelopment of an area or from applying varyingpressure by hand, which may adversely affect the desired printing image.Drying of the developer on certain portions of the plate before it canbe rubbed in to remove the undesired coating also may leave a residue onthe plate. A further difficulty with the hand method is in theapplication of the developing solution. It is presently the practice ofthe craftman to pour a quantity of developer onto a developing sponge orpad and onto the center of the plate, which quantity is supposedlysufficient to process the plate, and the craftman then works his spongefrom that reservoir. This procedure may lead to a high degree ofcontamination of the processing fluids by the removed photosensitivecoating as well as a change in the chemistry of the fluid because ofevaporation, which will, in turn, either reduce the efficiency of thechemistry, resulting in incomplete removal of the undesired coating inhighly critical areas of halftones, or increase its potency resulting inimage attack.

The present invention overcomes the difficulties associated withconventional hand developing of a plate coated on one side only byproviding a novel dispensing apparatus for lithographic developer. Thedispensing apparatus avoids changes in the processing solutions by aunique method of metering the processing fluids in controlled quantitiesonto the plate surface without damaging the plate surface, rendering itpossible to economically use the processing solutions only once, andwithout smearing or dragging used solutions into fresh solutions or ontoadjacent plate areas.

Prior to the present invention, there was no successful way to deposit aminimum amount of fluid automatically onto a printing plate for aone-time use of such fluid so that a machine operation was economical.Attempts were made to process plates by recirculating the fluids throughconventional spraying systems onto the surface of the plate and bydipping the plate into tanks of fluids, but it has been characteristicof many such fluids to become prematurely weakened by unavoidableaeration or by contamination of spent material from the non-image areas,resulting in a short period of time in an unusable solution. Further,when only small quantities of fluid are required to process a plate,such as one ounce of fluid per square foot of plate surface, it isessential to hold fluid consumption at this level in order to avoidextra costs.

The problem of metering small quantities of fluid over a large surfacearea is effectively overcome by the novel dispensing apparatus of thepresent invention. In the novel apparatus, fluid is pumped underpressure into a manifold, which may have a width of about one inch and aheight of about one-half inch. On the bottom of the manifold a pluralityof apertures dispense the fluid, under pressure created by a pump, intoa second bar which has a width of about one inch and a lengthcorresponding to the width of the machine. The bottom bar contains aslot which may have a width of about 1/16 inch, for example. The bar ismade of plastic so that it does not scratch the surface of the plate incontact therewith. The entire assembly is spring-loaded and rests on abackup plate made of hard rubber.

When the processing apparatus is actuated, a pair of nip rolls transporta plate into a developing station and between the backup plate and thedispensing apparatus. The pump pressure forces a quantity of developerinto the slot in the dispensing apparatus and, since there is a backupplate facing and in contact with the spring-loaded bar of the dispensingapparatus, the slot in the bar fills with developer prior to theentrance of the plate and causes a slight rising of the entire assembly,by about 0.015 inch. with little or no outflow of the developer. Thisrise, in turn, allows the plate to enter between the bar and the backupplate without actually contacting the dispensing apparatus.

As the moving plate receives fluid developer from the slot in the barand carries the developer away, the developer is constantly replacedfrom the manifold as a result of the pressure of the pump supplyingdeveloper from the reservoir. Simultaneously, this continuing feed ofdeveloper maintains the dispensing assembly above the surface of theplate to be developed and the inverted menicus created dispenses aminimum coating of developer, regulated by the pressure of the feedpump, uniformly upon the plate.

After passing the developing station, a reciprocating rubber squeegeeassures that the developer is adequately rubbed into the surface of theplate. By proper composition of the developer, the action thereof can bemade rather rapid so that shortly thereafter it can be squeegeed off anddrained away into a waste disposal by a pair of squeegee rolls.

A second application of developer, if required, may be applied in asimilar mechanism. A third similar mechanism can be employed to apply afixing solution, if necessary, for the proper preparation of the plate.This may be combined with a rubbing action of a piece of velour-likematerial reciprocating transversely to the direction of plate travel ata rate of about 175 strokes per minute. in a stroke of about one-halfinch. The plate then enters a washing station and a lacquering station,if required, followed by a second washing or gumming station beforeexiting from the apparatus as a completed plate ready for the printingpress or for further work prior to going to the printing press.

The invention will be further illustrated by reference to theaccompanying drawings in which FIG. I is a schematic view of aprocessing line for processing printing plates precoated on one sideonly,

FIG. 2 is a perspective view of a portion of the processing line of FIG.1 showing the developer dispensing apparatus, and

FIG. 3 is a sectional view taken on line 33 of FIG. 2 and looking in thedirection of the arrows.

Referring to FIG. I, a planographic printing plate sensitized on oneside and imaged by exposure to a desired master is inserted into theprocessing line at the point of the arrow 2. The inserted plate passesover the trigger mechanism 4 and thus actuates the entire processingline, i.e., the feed rolls as well as all transportsqueegee rolls beginrotating. Simultaneously, pumps connected to the various chemical supplytanks, not shown, begin operating and dispensing chemistry as required.Also the developer dispensing apparatuses or heads as well as therinse-scrubber head begin reciproeating.

The plate passes through a pair of feed rolls 6, which rolls pass theplate between the first developer dispens ing head 8 and its associatedsupport rail 10, and a controlled amount of developer at a controlledtemperature is dispensed from the developer dispensing head 8 onto theplate surface and carried away. This amount can be regulated byadjusting the pressure in the developer supply line by setting a bypass,not shown, and a volume regulator which will be described below inconnection with FIG. 3.

Inasmuch as the entire developer dispensing head reciprocates, and sincethe dispensing head has a spreader blade 12 attached thereto, chemistryis evenly spread over the entire surface of the plate and adequately andcompletely rubbed into the surface of the plate coating.

The plate then passes through a first set of transportsqueegee rolls 14which rolls transport the plate into the second developer dispensingassembly 16 having an associated backup plate 18. The construction ofthe second developer dispensing assembly 16 and its associated backupplate 18 is identical with the construction of the first developerdispensing head 8 and its associated backup plate 10.

The second developer dispensing head reapplies a fresh amount ofdeveloper solution in the same manner as the first developer dispensinghead 8. With this arrangement, a rapid and thorough development of theplate is obtained inasmuch as the "chemistry" is previously adjusted toprocess the exposed image within the time allowed by the speed of theplate travel and the distance between each set of rolls.

The plate then reaches a second pair of transportsqueegee rolls 20 whichremove all excess developer and, in turn, propel the plate under therinse-scrubber head 22 which removes residual developer from the platebefore it enters the third transport-squeegee roll assembly 24. Thelatter rolls advance the plate under the gum dispensing tube 26 and intothe transportsqueegee rolls 28, which latter move the plate between theair dryer tubes 30 and into the exit rolls 32 which, in turn, propel thedeveloped, gummed and dried planographic printing plate out of theprocessing line ready to be mounted on a press.

Referring to FIG. 2, a plate 34 is shown as it passes between the feedrolls 6 and under the first developer dispensing head 8. As will be seenfrom FIG. 2, developer is supplied through the developer line 36 and thedispensing head is reciprocated transversely to the direction of platetravel by means of the reciprocator shaft 38.

The dispensing head is shown in more detail in FIG. 3. The dispensinghead includes the bottom bar 40 which abuts against the hard rubbersurface 42 of the backup plate 10 when no plate is received between thetwo. The bottom bar 40 has a slot 44 therein which extends across thelength of the bottom bar 40 but not completely to the ends thereof, sothat developer pumped into the slot cannot run out of the ends thereof.The developer is supplied to the slot 44 by means of the passage 46which connects to the reservoir 48 in the manifold 50. The reservoir 48is connected to the developer supply line 36 by means of a bore in therod 52. The rod 52 slides freely in the supporting bracket 54, to whichthe reciprocator shaft 38 is connected by the machine screws 56, and theentire assembly is reciprocated by the shaft 38 connected to areciprocating apparatus, not shown.

The bar 40, which may be made of plastic, is biased against the surfaceof the plate 34 by means of the spring 58 and any degree of pressuredesired may be obtained by balancing the spring pressure against thepressure of the developer supplied to the slot 44.

The volume of developer supplied to the slot 44 may be regulated by thedeveloper supply volume regulator 60 having a hand wheel 62 thereon. Thesupply volume regulator is of conventional construction and,accordingly, will not be further described.

The entire processing line is enclosed in a housing, not shown.

The processing line is intended to be used with fresh chemistry at alltimes, i.e., there is no recirculation. By so doing, all parameters aremaintained constant and since, in addition, the temperature of thedeveloper is controlled to within 5F., processing of printing plates ispredictable and reproducible.

It will be obvious to those skilled in the art that many modificationsmay be made within the scope of the present invention without departingfrom the spirit thereof, and the invention includes all suchmodifications.

What is claimed is:

l. A dispensing apparatus for lithographic processing fluids,comprising; bar means adapted to extend across a printing plate to beprocessed, having a single outlet means comprising a slot in that sideof said bar means facing said plate to be processed and an inlet meansin fluid communication with said outlet means, mounted to moveperpendicular to the surface of said plate to be processed and normallybiased toward the side of said plate to be processed; means forsupplying processing fluid, under pressure sufficient to overcome thebiasing of said bar means and move said bar means away from the surfaceof said plate to be processed; and means for reciprocating said barmeans transversely to the direction of travel of said plate to beprocessed.

2. A dispensing apparatus according to claim 1 including spring meansbiasing said bar means toward a plate to be developed.

3. A dispensing apparatus according to claim 1 including spreader blademeans secured to said bar means.

4. A dispensing apparatus in accordance with claim 1 wherein the barmeans is biased toward the plate to be processed by means of a spring.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION PATENT NO.3,903,541

DATED September 2, 1975 I INVENTOR(S) Frederick W. von Meister andEugene J. Gaisser, Ir.

It is certified that error appears in the above-identified patent andthat said Letters Patent are hereby corrected as shown below: I

Item the name of. the third inventor, i.e. Robert C.

Graham, 10 Pierson Lane, Ptorham Park, New Jersey 07932 should bedeleted.

Signed and Sealed this Arrest:

RUTH C. MASON C. MARSHALL DANN Arresting Officer Commissioner of Parentsand Trademarks UNITED STATES PATENT OFFICE CERTIFICATE OF coRREcrrPATENT NO. I 3,903,541

DATED September 2, 1975 v INVENTOR(S) Frederick W. von Meister andEugene I. Gaisser, Ir.

It is certified that error appears in the above-identified patent andthat said Letters Patent are hereby corrected as shown below: a t

Item the name ofjthe third inventor, i.e. Robert C. Graham, 10 PiersonLane, Plorham Park, New Iersey 07932 should be deleted.

gigned and gcafied A nest:

RUTH C. MASON C. MARSHALL DANN Arresting Officer Commissioner nj'larentsand Trademarks

1. A dispensing apparatus for lithographic processing fluids,comprising; bar means adapted to extend across a printing plate to beprocessed, having a single outlet means comprising a slot in that sideof said bar means facing said plate to be processed and an inlet meansin fluid communication with said outlet means, mounted to moveperpendicular to the surface of said plate to be processed and normallybiased toward the side of said plate to be processed; means forsupplying processing fluid, under pressure sufficient to overcome thebiasing of said bar means and move said bar means away from the surfaceof said plate to be processed; and means for reciprocating said barmeans transverseLy to the direction of travel of said plate to beprocessed.
 2. A dispensing apparatus according to claim 1 includingspring means biasing said bar means toward a plate to be developed.
 3. Adispensing apparatus according to claim 1 including spreader blade meanssecured to said bar means.
 4. A dispensing apparatus in accordance withclaim 1 wherein the bar means is biased toward the plate to be processedby means of a spring.